Electrical apparatus



Jan. 26, 1937. R BEMAN 2,069,003

ELECTRI CAL APPARATUS Filed Feb. 18, 1955 INVENTOR.

Ply/mam hf Elem/w ATTORNEY Patented Jan. 26, 1937 ELECTRICAL APPARATUSRansom H. Beman, Detroit, Mich assign'or to Kelvinator Corporation,Detroit, Mich., a corporation of Michigan Application February 18, 1935,Serial No. 7,104

5 Claims.

My invention pertains to time delay safety devices and more particularlyto safety control devices for oil burner systems.

It is an object of my invention to provide a safety control devicecomprising an iron structure and means for heating the same by thehysteresis and eddy current losses induced therein by an alternatingmagnetic field set up by an initiated operation for actuating athermally associated thermostatic device, a predetermined timethereafter and having means for opposing and neutralizing the magneticfield in response to a succeeding operation whereby the operation of thethermostatic device is avoided.

It is a further object of my invention to provide a time delay safetycontrol device comprising a thermostatic switch heated by anelectromagnetic solenoid comprising an iron core slidably disposedtherein whereby the time characteristics and the impedance of the devicein the controlled circuit may be adjusted.

It is also an object of my invention to provide a variable impedancetime delay safety'device for use in alternating current circuitscomprising a thermostatic device heated by variable impedance meansenergized in motor circuit and including opposing electromagnetic meanswhich is adapted to be subsequently energized under normal operatingconditions to prevent the continuation of the heating of thethermostatic element to deenergize the motor.

The invention itself, however, both as to its organization and itsmethod of operation, together with additional objects and advantagesthereof, will best be understood from the following description ofspecific embodiments, when read in conjunction with the accompanyingdrawing, in which:

Fig. 1 is an elevational view of an embodiment of my time delay safetycontrol device partially in section; and

Fig. 2 is a diagrammatic view representing a system controlled by mysafety device.

Referringmore particularly to Fig. 1 of the drawing my safety controldevice comprises a bobbin structure I of non-magnetic material, suchrubber or brass for example, for supporting a pair of separatelyinsulated solenoid windings 3 and 5 thereon. The coil supporting bobbinI maybe mounted upon a bracket 1 projecting from a. suitable instrumentboard or panel'S and it is of spool like conformation having an apertureI extending axially therethrough for slidably receiving a core member IIofsome magnetizable material such as iron. An adjusting screw I3 isthreadably supported in a bracket l projecting from the panel 9 underthe lower end of the core whereby its insertion into the bobbin I may beadjusted. The lower end of the core is preferably provided with alaterally projecting flange ll for positively limiting its insertioninto the winding.

The upper end of the bobbin I is provided with upwardly projectingflanges I9 upon which a thermostat 2| comprising a bimetallic element issupported across the upper end of the core. The bimetallic element 2!may consist of a pair of connected flat strips of unlike metal, or if aquick snap action is desired, it may be composed of a pair of cup shapeddiscs of unlike metal firmly secured together. If the material of thesolenoid bobbin is a poor heat conductor, such as rubber or a phenoliccondensation product, the core receiving aperture I0 may be extendedthrough the upper end thereof to permit the core I I to be elevated intointimate thermal coupled relation with the bimetallic element 2|. If thebobbin structure is of some non-magnetic metal such as brass or copperthe entire structure will be heated from the iron core thereby heatingthe thermostatic element 2|. in

Although my safety control device may be utilized for regulatingmechanical elements, it is especially suitable for controllingelectrical apparatus which is accomplished by a pair of electricalcontact members 23 and 25 supported in engageable relation on resilientmetallic arms 21 and 29 mounted in electrically insulated relation on abracket 3 la projecting from the panel board. The lower extended ends ofthe separate contact supporting arms 2'! and 29 are provided withrounded loops 3!! for smoothly engaging the adjacent end of a. wedgeshaped actuating member 3I which is slidably mounted in a bracket 33projecting from the panel. The contact actuator 3| 40 is disposed forfree slidable movement through the bracket 33 and its lower end isprovided with a smooth spherical terminal 35 for operatively engagingthe bimetallic member. A compressional spring 36 may be concentricallydisposed on the actuator 3| for reacting between the bracket I 33 andthe flange of the spherical terminal 35 for continuously biasing itdownwardly. When the actuator is elevated by distortion of thebimetallic member, its uppermost end spreads apart the contactsupporting arms thereby disengaging the contacts and interrupting anyelectrical circuit associated therewith. It will be understood that amechanical regulating mem- II is permanently connected through anotherconductor 42 to one end of the other separately insulated winding 5 onthe bobbin l. The other terminal 43 is connected jointly to the otherends of the two windings by permanently connected conductors 44 and 45.

My safety controller may be advantageously utilized for controlling asystem wherein a certain operation must successfully follow an initiatedoperation and upon the failure thereof the initiated operation must bepromptly terminated; Such a. system may comprise an oil burner controlsystem, as shown in Fig. 2. In the operation of such a system thedecrease of ambient temperature to a predetermined degree causes hillthe energization of a blower motor M which throws a blast of oil sprayinto an associated furnace (not shown). Normally'the oil spray issuccessfully ignited by a continuous burning pilot flame or an electricspark, in a well known manner, and the oil spray is consumed as itenters the furnace. It is necessary however to provide for thecontingency of failure of ignition which might be caused by extinctionof the pilot flame or other conditions. For this purpose I provide athermo responsive stack switch 56 which comprises a spiral bimetallicelement 56 disposed in the stack, or closely associated therewith, forrotating a disc 53 operatively connected with anesible contact arm 55carrying a contact 56 toward or away from a stationary contact 58mounted adjacent thereto. The stack operated electric contacts and iiiare electrically connected by conductors ill and $3 to the terminals diand so respectively connected to the separated ends of the separatewindingson the safety control de vice.

in operation decreasing room temperature causes the room thermostat 6'!to close its contacts thereby completing-a circuit to energize theblower motor M from the alternating current service mains Li and L2. Themotor energizing circuit may be traced from main line conducto? Llthrough a conductor 59 to the contacts $59 of the room thermostat 51 andthrough a conductor 6! to terminal 39 on the safety controller thence tothe winding 3 on the bobbin, and from the other end of the winding 3 byway of conductor 35 to the terminal connector 63, through a conductor 65to the thermostatically controlled contacts 25 and 23 on the safetycontroller thence by way of a conductor 61 to the motor M and from theother terminal of the motor through a conductor 69 to the other mainline conductor L2.

As the motor starts up it drives a suitable oil throwing blower or unitit which supplies a blast of oil spray to a furnace or other heatingdevice (not shown).

In response to normal ignition of the flame the rising temperaturevariations afiect the stack switch to close its contacts and 58 within avery short time alter the blower motor M has started. This connects thetwo separate wind ings i3 and in parallel relntionior simultaneousenergization in the motor circuit.

The separate windings 3 are coiled in opposing relation or are soconnected into their respective circuits that their magneto-motiveforces'oppose and neutralize, and when both are energized simultaneouslythe heating effects or? eddy currents andhysteresis losses in the coreii are eliminated. Hence, normally the ironcore structure is subjectedto the heating effect of the alternating magnetic field for only a veryshort time until the subsequent energization of the second winding inopposed parallel relation neutralizes this effect.

When. the pilot flame fails, or other conditions arise which cause theflame failure when the blower motor starts, the stack switch will notreceive heat and consequently will not close its thereby opening themotor circuit and stopping Q the blower. This operation prevents thedanger ous and undesirable conditions which would he caused bycontinuously supplying unignited oil or gas to the furnace.

Although the thermostatic stack switch re sponds promptly to the risingtemperature in the stack, an appreciable time interval must he cl lowedfor this efiect to take place after the blower motor M has started...This is readily accomplished by adjusting the time intervals ofoperation the safety control device by'turning the adjus able stop screwit under the iron core ll As the core ii is projected upwardly into thewinding, the heating efiect of the alternating magnetic held isincreased, and the thermo coupling of core it with the bimetallicelement 25 is also in= creased, thereby reducing the time interval re=ouired between the closing of the motor circuit by the room thermostat5i and the reopening oi the circuit by the safety device. iii it is desired to lengthen this time interval, this is r 1 lg; accomplished byadjusting the threaded stop member (13 to lower the iron core ll.metallic element it is of the quick snap acting type, it separates theelectric contact members 23 and 25 quickly when the stack switch failsto close after a predetermined interval.

By adjusting the position of the iron core it within the windings 3 and5 the impedance of the winding 3 in the motor circuit may also he variedto match the characteristics of the cir cuit. "lihis adjustment 'mayalso be utilized to vary the circuit characteristics, to compensate forvarious motor loads or to compensate for different alternating currentfrequencies. In manner my device may be adjusted in eccord-= ance withthe particular installation in which the device is used.

it will be seen that I have provided a simple,

positive acting, time delay safety control device ill desire to limitthe invention structions herein set forth;

I claim as my invention:

1. In combination a heat -responsive device, means actuated thereby,means for controlling said device comprising a member of magnetizablematerial, said material being in heat exchange relation with the heatresponsive device, a source of magneto-motive force adjacent thereto,and a, source of opposing magneto-motive force for opposing andneutralizing the effect of said first source in the, vicinity of saidmember.

2. In combination a heat responsive device, means actuated thereby,heating means for controlling said device comprising a thermally coupledmember of magnetizable material, said material being in heat exchangerelation with the heat responsive device, an adjacent source ofalternating magneto-motive force for heating said member by inducingeddy current and hysteresis losses therein, and means for varying therate of heating said device.

3. In combination a heat responsive device, means actuated thereby,heating means for controlling said device comprising a thermally coupledmember of magnetizable material, said material being in heat exchangerelation with the heat responsive device, an adjacent source ofalternating magneto-motive force for heating to the exact consaid memberby inducing eddy current and hysteresis 1 losses therein, means forvarying the rate of heating said device, and an opposing source oilalternating magneto-motive force for neutralizing and eliminating theeffect of said first source in thevicinity of said member.

4. In combination in a, variable impedance time relay controller, a heatresponsive actuator; control means actuated thereby; heating means forsaid actuator comprising a thermally coupled member of magnetizablematerial, an adjacent source of magneto-motive force, means for varyingthe rate of heating said actuator; and an opposed source ofmagneto-motive force for limiting the heating efiect of said firstsource in the vicinity of said member.

5. In combination in a variable impedance time delay controller, asnapacting heat responsive device comprising cupped discs of unlike metal,control means actuated thereby, heating means for operating said devicecomprising a thermally coupled member of magnetizable material, anadjacent source of alternating magneto-motive force, adjustable meansfor varying the rate of heating said device, and an opposing source ofalternating magneto-motive force for neutralizing and eliminating theeffect of said first source in the vicinity of said member.

RANSOM H. BEMAN.

